/*
 * Alloy Analyzer 4 -- Copyright (c) 2006-2008, Felix Chang
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package edu.mit.csail.sdg.alloy4;

/**
 * Immutable; this is the abstract super class of the various possible errors.
 *
 * <p><b>Invariant</b>:       pos!=null && msg!=null
 */

public abstract class Err extends Exception {

    /** This stores the filename/line/row information (Pos.UNKNOWN if unknown). */
    public final Pos pos;

    /** The actual error message. */
    public final String msg;

    /**
     * Constructs a new Err object.
     * @param pos - the filename/line/row information (can be null if unknown)
     * @param msg - the actual error message
     * @param ex - if nonnull, it will be recorded as the cause of this exception
     */
    Err(Pos pos, String msg, Throwable ex) {
        super((msg==null ? "" : msg), ex);
        this.pos = (pos==null ? Pos.UNKNOWN : pos);
        this.msg = (msg==null ? "" : msg);
    }
}
